Formative cells of calcifying tissues are known to be responsible for synthesis and secretion of their organic components. The same cells are implicated in certain aspects of mineralization but with little direct evidence to explain their role. Calcium, in addition to being involved in mineralization, exerts regulatory influence on many metabolic processes including secretion and enzyme activation. The secretory ameloblast is a polarized cell with discrete regions of secretory activity at its distal extremity where new enamel crystallites form. Smooth and ruffle-ended maturative ameloblasts are associated with mineralization and protein removal from adjacent maturing enamel. Calcium interactions in ameloblasts will be investigated by using model systems in which agents are injected which disturb enamel physiology to varying degrees. The series of agents will include fluoride, cobalt, strontium, tetracycline, colchicine and vinblastine. By applying specific criteria for evaluating the effects of these agents, model systems will be indentified in which secretion, initial crystal formation or overall mineralization is selectively inhibited. The detailed effects of these agents on ameloblast functions will be analysed by a multimethod approach comprised of 1) energy dispersive x-ray spectroscopy (EDS) microanalysis and Ca45 autoradiography to determine calcium levels in specific cell layers, 2) ultrastructural examination for morphologic changes in cells, enamel precursors and forming enamel crystals, 3) potassium pyroantimonate and enzyme cytochemistry, EDS microanalysis, electron energy loss spectroscopy (EELS) and H3-Trytophan autoradiography to follow the distribution and activities of key elements, enzymes and precursors in relation to the ameloblasts and their functions. Follow-up time and dosage studies will verify specific relationships between the various parameters. The long-term objective is to advance our understanding of the interactions of calcium and hard tissue forming cells as well as the mechanisms of biological mineralization. Such understanding is essential for prevention and treatment of many diseases.